Usage:
Empire Formation of Ravalli Group of Belt Supergroup (MT*)
Geologic age:
Middle Proterozoic*
Type section, locality, area and/or origin of name:
Type localities are on ridge north of Empire [2 mi west of Marysville] and in canyon walls just below Marysville, Lewis and Clark Co., west-central MT. Named from exposure west of Empire Mine, at head of Lost Horse Gulch in western part of Marysville district, Lewis and Clark Co., west-central MT (Walcott, 1899; see also Knopf, 1950).
Formation was found to be best exposed in section that extends east-west through USGS benchmark 4450 in Scratchgravel Hills, northwest of Helena (see Knopf, 1950).
AAPG geologic province:
Northern Rocky Mountain region*
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).